1. Modems in a POWERLOGIC System
Modbus RTU to Modbus ASCII
February 2002

2. What’s the Issue? Modbus RTU Modem Communications Modbus ASCII
is a time delimited serial protocol
a period of 3.5 character times without a character identifies the end of a message 19.2k)
Modem Communications
character timing of messages transmitted via modems is extremely unpredictable
results in communications errors (typically CRC)
Modbus ASCII
this protocol is more tolerant of time delays between characters in a message (up to 1-second)
none of our current products or software support this protocol
messages are approximately twice as large as RTU messages
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3. Is there a Solution? Present Solution
Install an interface device between each modem to convert from Modbus RTU to Modbus ASCII
This maintains a Modbus RTU connection to the devices and to SMS while Modbus ASCII is used between the modems
Requires a constant connection
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4. What Does This Look Like?
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5. What If I Need Ethernet?
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6. MUCM Info
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7. QUCM Info http://www.niobrara.com/ftp/manuals/pdf/mucm_qucm.pdf
The QUCM comes out the box in a non-functional state
You must load an image into the QUCM prior to configuration
Connect PC serial port to QUCM port 1 using NR&D “MM1” cable
Copy the ZIP file from the supplied floppy disk and copy to a known directory on you PC
Un-ZIP the files
From a “command prompt” enter “ZAPREG32 com1:9600,e,8, b”
A window will open with a “Read / Write Register” interface
Enter the desired IP Address in Registers
Enter the desired Subnet Mask in Registers
Enter the desired Default Gateway in Registes
Press “ESC” to exit
From the “command prompt” enter
“QLOAD 1 QRPCTCP.QCC IPAddressEnteredAbove -a”
Now place both switches, next to serial ports, to “RUN”
From a “command prompt” enter MEBSW
The window above will appear
Press “S” to enter the “Setup” screen
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